Battery-life and Output Radio Frequency Spectrum (ORFS) are two important criteria for determining the performance of a mobile terminal, such as a mobile telephone or the like. Both battery-life and ORFS may be adversely affected by a varying Voltage Standing Wave Ratio (VSWR) at the output of a power amplifier in the transmit chain of the mobile terminal. The VSWR may vary due to environmental factors such as the user placing an antenna of the mobile terminal near his or her body. As a result of the varying VSWR, the load impedance seen at the antenna also varies from an ideal load, such as 50 ohms.
For open loop power amplifiers, the variations in VSWR cause the output power of the power amplifier to deviate from the target output power. This deviation from output power decreases the quality of service (QoS), increases the probability of dropped calls in fringe areas, increases the liability of mobile terminal manufacturers in terms of tolerated output power versus Specific Absorption Ratio (SAR), and increases the peak current of the power amplifier. Thus, there remains a need for power amplifier control circuitry that reduces or eliminates output power variations due to variations in load impedance.